A patent for invention is disclosed in the Chinese patent database in the Nov. 17, 2008 with application number ZL200820016925.5 named a flow rate controller. The controller is disposed with a body disposed with a groove, an inlet disposed in the body and an outlet, a switch button a and a switch button b disposed inside the body, a restoring spring, a constant pressure sealing ring, a water diversion body with an outlet hole and outlet, a sealing ring and a switch button disposed in the switch button a; the switch button a is engaged to the switch button b, the restoring spring, the constant pressure sealing ring and the water diversion body are disposed below the switch button b, the sealing ring is disposed below the water diversion body; the flange at the upper end of the switch button b can be slide along the groove of the body, the flange can withstand the bottom of the rib beside the groove; similarly to a spring ball point pen control way, the flow rate is controlled by the on-off of the outlet controlled by the switch button a and the switch button b; it can be assembled in the handle of the shower or the outlet, the front end or back end of a shower tap, the flow rate can be switched rapidly by the switch button. However, it has disadvantages as below: 1. the sliding direction of the switch button is vertical to the water flowing direction, so that the controller increases the space occupied, especially in a shower; 2. the sliding direction of the switch button is vertical to the water flowing direction, so that it needs more pressure force.